The devices described below relate to the field of electro-acupuncture and non-invasive stimulation of nerves.
We have developed an electro-acupuncture or nerve stimulation device which has proven effective for the control of nausea and vomiting. The basic device is described in Bertolucci, Nausea Control Device, U.S. Pat. No. 4,981,146 (Jan. 1, 1991). The device, marketed under the trademark Relief-Band(copyright), is worn on the wrist like a wristwatch, with a watch-like housing which is positioned on the underside of the wrist. The housing has two electrodes on the inside face (the face in contact with the wrist when secured to the wrist), a battery and circuitry inside the housing, and control buttons on the outer face. A patient suffering from nausea or vomiting (from motion sickness, morning sickness, chemotherapy, or anesthesia) can strap the device onto their wrist and turn it on. When turned on, the device emits an electrical stimulation pulse over the P6 acupuncture point (corresponding to the superficial course of the meridian nerve through the wrist). Within several minutes, most patients experience a substantial relief of nausea. The device uses non-invasive nerve stimulation whereby electricity is passed through the electrodes to stimulate nerves located on the ventral side of the wrist (this anatomical position is sometimes referred to as the palmar side of the wrist). The treatment provided by the device is sometimes referred to as electro-acupuncture, which is a form of acupuncture, and the ventral site of application is referred to in the acupuncture art as the P6 point, pericardium 6 point, or master point of the pericardium meridian (sometimes referred to as the vascular meridian). It is also portable, self-contained and convenient to the patient. Electrical pulse repetition rate of approximately 70 pulses per second and a pulse width of 80 microseconds have been found to provide effective relief of nausea in a patient. Our currently preferred electrical pulse pattern comprises about 350 microsecond pulse width at about 31 pulses per second at power levels of about 10-35 milliamps peak pulse height. Thus a wide range of pulse patterns may be used in non-invasive nerve stimulation devices.
In each of our electro-acupuncture products, the stimulation and effect are greatly enhanced if the patient applies a gel to the skin before strapping the device onto the wrist. This gel serves as an electronic to ionic current conversion layer between the electrodes and the dry outer skin layer. This electrical conduction layer, sometimes referred to as an impedance matching layer, greatly enhances the effect of the device and lowers the power requirements for the device. The patient applies the gel to the skin before strapping the device onto the wrist. The gel may be referred to as a conductivity gel or an electro-medical coupling agent. The users may use too much gel, too little gel, or apply it too infrequently. Some users may omit application of the gel, either through forgetfulness or ignorance of need to use it. Additionally, gel may be removed by water in the environment of use, such as where the device is used for seasickness on a small sail boat while the user is operating the sail boat.
The devices and methods described below provide a nerve stimulation or electro-acupuncture device which may be used without the application of conductivity gel, or with minimal application of conductivity gel. The nerve stimulation device comprises a housing preferably shaped like a wristwatch that can be strapped to a patient""s wrist about the P6 acupuncture point. The housing houses the control circuitry and a battery. The nerve stimulation device includes two D-shaped electrodes connected to control circuitry and the battery. The pair of electrodes is mounted to the inner face of the housing, so that they rest over the P6 acupuncture point when the housing is worn on the patient""s wrist. The D-shaped electrodes effectively provide stimulation to the patient without the need for additional application of conductivity gel or impedance matching material. The nerve stimulation device also comprises a gasket made of an electrically non-conductive material such as neoprene or silicone. The gasket includes two apertures sized and shaped to receive the electrodes when the gasket is applied to the device. The gasket provides electrical insulation between the electrodes so as to prevent a short circuit between the electrodes. The gasket also acts as a seal between the electrodes and the patient""s wrist to seal in conductivity gel or other conductive material. It will also serve to retain perspiration in amounts sufficient that the perspiration itself serves as the conductive material.